Morning, fasting, twice
The Endocrine Society's guidance is at least two early-morning, fasting tests before anyone calls it low.1 The American Urological Association says the same: two total testosterone measurements, on separate occasions, both early in the morning.2
One test is a reading. Two is a pattern.
What to ask for
The Endocrine Society's statement refers to both total and free testosterone, accurately measured.1 Ask for both, and ask the doctor to explain what the lab's reference range means for you.
What counts as low
The AUA uses a total testosterone below 300 ng/dL as a reasonable cut-off in support of a diagnosis of low testosterone.2 Irish labs usually report nmol/L: 300 ng/dL is about 10.4 nmol/L.
The number isn't the diagnosis on its own. Hypogonadism means symptoms plus consistently low results.1
Getting it done in Ireland
Your GP can order it. Book the earliest slot you can get, don't eat beforehand, and ask for a repeat if the first result comes back low.
Private at-home kits exist. If you use one, take the sample early in the morning, fasted, repeat it, and bring both results to a doctor. A kit result is a number, not a diagnosis.
If nothing's wrong, a test won't tell you much
There isn't enough evidence to screen men who have no symptoms.1 If you feel fine, one test on its own won't tell you much.
Tracking a change is different. If you're overhauling how you eat, train and sleep, talk to your GP about a baseline and a repeat twelve weeks later — same lab, same time of morning — so you can see whether anything moved.
If it comes back low
Low twice, with symptoms, is a conversation for your GP or an endocrinologist — not a supplement shop. Before anyone prescribes, they'll look at reversible causes like weight and medications.1